Reconstitution stratigraphique et paléogéographique du Jurassique inférieur et moyen à partir des olistolithes inclus dans la Formation de Kotel (Stara Planina orientale, Bulgarie)

P. Tchoumatchenco. Stratigraphic and palaeogeographic reconstruction of the Lower and Middle Jurassic based on olistoliths embedded in the Kotel Formation (Eastern Stara Planina, Bulgaria). The Kotel Olistostrome Formation in the Eastern Stara Planina contains olistoliths of various Jurassic rocks grouped in four facial types corresponding to different palaeogeographic areas of the ancient basin where the rocks were originally formed. These are the facial types of Bilka, Djula, Karaveljovo and Čerkovište. The Bilka facial type was formed in a lagoon. It consists of pink aphani te limestones overlying transgressively Upper Triassic reef and subreef limestones. They are of Pliensbachian age. The upper part of their overall section is crosscut by Toarcian-Middle Jurassic neptunian dykes containing numerous brachiopods. The Djula facial type was formed in the sublittoral zone dominated by a high-energy environment involving tidal and bottom curents. It consists mostly of grey-black or red detrital limestones overlying transgressively Middle and Upper Triassic carbonates. The transgression involved quartz sandstones. The top of the cumulative section consists of grey-black aleuritic argillites and aleurolites. The age of this facial type range from the Sinemurian to the Bajocian. The Karaveljovo facial type was formed as a bar on the shelf in a high-energy environment dominated by a strong bottom current. It consists of Domerian-Toarcian biodetritical marls and limestones. The underlying rocks are not known. The Čerkovište facial type was formed in the environment of the open-sea shelf and probably in the upper part of the epibathial zone. It consists of red aleuritic marls and limestones whose age ranges from the Sinemurian to the Toarcian. The underlying rocks are not known.